So I have this 900+ polylines in a hosted feature layer and I'm editing/updating from arcgis pro(2.6.0)
The layer has a subtype and seven or eight coded value domains.
When attempting to split a line (an action which I have done numerous times before) I get:

The [CreationDate_1] isn't the subtype column and has no domain, also it is nullable. the field type is 'date' as expected.
As I said, this has been working before so I suspect some sort of corruption.
I created a local copy ('feature class to feature class' conversion tool) and when I edit a line in that layer I can't see the attributes in the attribute pane (but they are present and editable in the attribute table). So I'm not very eager to overwrite the weblayer to 'test'.
Next I will try to export the hosted feature layer to a shapefile and open that, perhaps using arcmap. Not very happy missing this deadline.
And when creating a new line:

seems like another attribute though? CreationDate in stead of CreationDate_1 ??
Does anyone recognise this? Any idea's on how to solve it? Support case has been filed.
Thanks for your time, regards, Bert